NCERT Solutions for Class 11 Biology Chapter 19 Chemical Coordination and Integration

NCERT
SOLUTIONS
CLASS - 11th

aglase .co

Class : 11th
Subject : Biology
Chapter : 22
Chapter Name : Chemical Coordination And Integration

Q1 De ne the following:
(a) Exocrine gland
(b) Endocrine gland
(c) Hormone

Answer. (a) Exocrine glands: Glands that discharge secretions into ducts are known as exocrine
glands. Sebaceous gland in the skin, salivary gland in the buccal cavity, etc. are examples of
exocrine glands.
(b) Endocrine glands: Glands that do not discharge their secretions into ducts are known as
endocrine glands. Instead, these glands discharge their secretions directly into the blood. Pituitary
gland, thyroid gland, adrenal gland, etc. are examples of endocrine glands.
(c) Hormones: Hormones are chemical messengers that regulate physiological processes in living
organisms. They act upon speci c cells/tissues/organs which are called target cells/tissues/organs.

Q2 Diagrammatically indicate the location of the various endocrine glands in our body.

Answer. The location of various endocrine glands in the human body can be illustrated as follows:

Q3 List the hormones secreted by the following:
(a) Hypothalamus
(b) Pituitary
(c) Thyroid
(d) Parathyroid
(e) Adrenal
(f) Pancreas
(g) Testis
(h) Ovary
(i) Thymus
(j) Atrium
(k) Kidney
(l) G-I Tract

Answer. (a) Hypothalamus: Hormones secreted by the hypothalamus include:

(1) Releasing hormones: These hormones stimulate the secretions of the pituitary hormone.
Examples of these hormones are:
(i) Gonadotrophin-releasing hormone
(ii) Thyrotrophin-releasing hormone
(iii) Somatotropin-releasing hormone
(iv) Adrenocorticotrophin-releasing hormone

(2) Inhibiting hormones: These hormones inhibit the secretions of the pituitary hormone.
Examples of these hormones are:
(i) Somatostatin
(ii) Growth-inhibiting hormone
(iii) Melanocyte-inhibiting hormone

(b) Pituitary: The pituitary gland has two components i.e., adenohypophysis and
neurohypophysis.
Hormones secreted by the adenohypophysis are:
(i) Growth hormone (GH)
(ii) Prolactin
(iii) Thyroid-stimulating hormone (TSH)
(iv) Adrenocorticotrophic hormone (ACTH)
(v) Luteinizing hormone (LH)
(vi) Follicle-stimulating hormone (FSH)
(vii) Melanocyte-stimulating hormone (MSH)

Hormones secreted by the neurohypophysis are:

(i) Oxytocin

(ii) Vasopressin
(c) Thyroid: The thyroid gland secretes three hormones namely, thyroxin, triiodothyronin, and
calcitonin.
(d) Parathyroid: The parathyroid gland secretes a hormone known as the parathyroid hormone.
(e) Adrenal: The adrenal gland is divided into two parts, the outer adrenal cortex and the inner
adrenal medulla.

Hormones of adrenal cortex include the following:
(i) Mineralocorticoids: The hormone secreted is known as aldosterone.
(ii) Glucocorticoids: The hormone secreted is cortisol. Hormones of adrenal medulla are
adrenaline and nor-adrenalin.

(f) Pancreas: Hormones secreted by the pancreas are insulin and glucagon.
(g) Testis: The hormone secreted by the testis is testosterone.
(h) Ovary: The hormone secreted by the ovary includes estrogen and progesterone.
(i) Thymus: Hormones secreted by the thymus are thymosins.
(j) Atrium: The walls of the atrium secrete atrial natriuretic factor.
(k) Kidney: The hormone secreted by kidney is erythropoietin.
(l) G-l tract: The hormones secreted by the G-l tract are Gastrin, secretin, cholecystokinin (CCK),
and gastric inhibitory peptide (GIP).

Q4 Fill in the blanks:

Answer. (a) Pituitary
(b) Thyroid
(c) Adrenal
(d) Ovary, Testis
(e)Melanocyte

Q5 Write short notes on the functions of the following hormones:
(a) Parathyroid hormone (PTH)
(b) Thyroid hormones
(c) Thymosins
(d) Androgens
(e) Estrogens
(f) Insulin and Glucagon

Answer. (a) Parathyroid hormone (PTH) — The parathyroid hormone is secreted by the
parathyroid gland. Its main function is to increase the level of calcium in blood. It promotes the
reabsorption of calcium from nephrons and also, promotes the absorption of calcium from
digested food. Hence, it plays an important role in maintaining calcium balance in the body.
(b) Thyroid hormones — Thyroid hormones such as thyroxine, triiodothyronin, and
thyrocalcitonin are secreted by the thyroid gland. Thyroxine maintains the basal metabolic rate of
the body and regulates the carbohydrate, fat, and protein metabolism. Water and electrolyte
balance is also maintained by thyroid hormones. Thyrocalcitonin or calcitonin lowers calcium
level in blood plasma. It plays a signi cant role in calcium levels along with parathyroid hormone.
(c) Thymosins — Thymosin is secreted by the thymus gland. It plays a major role in protecting the
body against infectious agents. It helps in the differentiation of T-lymphocytes and also promotes
the reproduction of antibodies. Hence, it provides both cell-mediated and humoral immunity.
Thymosins also help in the development of sex glands.
(d) Androgens — The leydig cells of testis produce androgens such as testosterone. Testosterone is
a male sex hormone that regulates the development of secondary sex characteristics such as facial
hair, hoarse voice, development of reproductive organ, etc. Androgens also regulate the
development, maturation, and functions of various male accessory organs such as epididymis and
prostate glands. It stimulates spermatogenesis and formation of mature sperms. It also in uences
male sexual behaviour.
(e) Estrogens- Estrogen is the female sex hormone that controls the development of secondary sex
characteristics such as enlargement of breasts and development of female reproductive organs. It
plays a role in the development, growth and maturation of female secondary characteristics. It
also helps in the development of growing ovarian follicles. It in uences female sexual behaviour.
(f) Insulin and glucagon — Glucagon and insulin are secreted by cells of pancreas. They regulate
the blood glucose level in the body. a-cells secrete glucagon that maintain a normal blood glucose
level in the body, whereas ß-cells secrete insulin that regulates the storage of glycogen in the liver.
Function of insulin — Insulin stimulates glycogenesis (conversion of glucose to glycogen). The
rapid conversion of glucose from the blood to glycogen in hepatocytes and adipocytes results into
a decreased glucose level. Insulin also prevents the formation of glucose from non-carbohydrate
substances such as proteins and fats. Hence, it acts as a regulator of carbohydrate metabolism.
Function of glucagon — The main function of the glucagon is to increase the level of glucose when
there is a de ciency of glucose in the body. This process is known as glycogenolysis.

Q6 Give example(s) of:
(a) Hyperglycemic hormone and hypoglycemic hormone

(b) Hypercalcemic hormone
(c) Gonadotrophic hormones
(d) Progestational hormone
(e) Blood pressure lowering hormone
(f) Androgens and estrogens

Answer. (a) Hyperglycemic hormone and hypoglycemic hormone: Hyperglycemic hormone is
glucagon, while hypoglycemic hormone is insulin.
(b) Hypercalcemic hormone: Parathyroid hormone (PTH) is hypercalcemic hormone.
(c) Gonadotrophic hormones: Luteinizing hormone and follicle stimulating hormones are
examples of gonadotrophic hormone.
(d) Progestational hormone: Progesterone is a progestational hormone.
(e) Blood pressure lowering hormone: Nor-adrenalin is a blood pressure lowering hormone.
(f) Androgens and estrogens: Testosterone is an example of androgen, while an example of
estrogen is estradiol.

Q7 Which hormonal de ciency is responsible for the following:
(a) Diabetes mellitus
(b) Goitre
(c) Cretinism

Answer. (a) Diabetes mellitus is characterized by abnormally high glucose levels in the blood due
to the de ciency of hormone, called insulin.
(b) Goitre is characterised by an abnormal enlargement of the thyroid gland due to the de ciency
of thyroxin hormone in the body.
(c) Cretinism is characterized by stunted growth in the baby due to the de ciency of thyroid
hormone in the body.

Q8 Brie y mention the mechanism of action of FSH.

Answer. Follicle stimulating hormone (FSH) is secreted by the pars distalis region of the anterior
pituitary. It regulates the development, growth, and reproductive processes of the human body. In
the ovary, FSH stimulates the growth and maturation of ovarian follicle. As the follicle grows and
matures, it releases an inhibitory hormone known as inhibin that ends the process of FSH
production. Action of FSH: Follicle stimulating hormone produces its effect by binding to its
speci c receptors present on the ovarian cell membrane. Binding of FSH hormone to its receptor
leads to the formation of hormone receptor complex. The formation of this complex leads to
biochemical changes in the ovarian follicle, present in the ovarian. The ovarian follicles mature
and release a mature ovum in the fallopian tube for fertilization.

Q9 Match the following:

Answer.